第3题: [单项选择]在生物碱的氯仿提取液中,加酸调pH由高至低的酸性缓冲液依次萃取,最先得到() A. 弱碱性生物碱 B. 近中性生物碱 C. 酸碱两性生物碱 D. 强碱性叔胺生物碱 E. 以上都不是 参考答案:A 答案解析:在生物碱的氯仿提取液中,加酸调pH由高至低的酸性缓冲液依次萃取,最先得到弱碱性生物碱,所以答案为A。
A. The speaker likes his sales program. B. The speaker is satisfied with his pay. C. The speaker feels bored and dull. D. The speaker has to pay for his products. 参考答案:B 答案解析:[听力原文] I have to sell the same products all the time, which is sometimes dull and boring. But by